Gravitational waves detected for third time

An international team of scientists including 21 researchers from The University of Western Australia has detected gravitational waves for the third time in history, following their world-first discovery in September 2015 and second detection in December 2015.

Gravitational waves are waves of energy, ripples in the fabric of space-time. The discovery of the first wave proved a prediction by Einstein 100 years ago.

The newfound black hole, formed by the pair’s merger, has a mass about 49 times that of our Sun. This fills in a gap between the masses of the two merged black holes detected previously by LIGO, which had solar masses of 62 (first detection) and 21 (second detection).

These collisions produce more power during the instant before the black holes merge, than is radiated as light by all the stars and galaxies in the universe at any given time. The recent detection is the farthest yet, with the black holes located about 3 billion light-years away. (The black holes in the first and second detections are located 1.3 and 1.4 billion light-years away, respectively.)

The third and most recent detection, called GW170104, was made on January 4 2017 and described in a new research paper published in the journal Physical Review Letters.

The latest finding solidifies the case for a new class of black hole pairs, or binary black holes, with masses that are larger than what had been seen before by the Laser Interferometer Gravitational-wave Observatory (LIGO) detectors.

Professor David Blair, from UWA’s School of Physics, said the event released more energy in its last few orbits than that of rest of the entire universe.

“Yet when the ripples passed the LIGO detector they made it vibrate by just one attometer, or 0.000000000000000001 metres,” Professor Blair said.

Despite this tiny displacement, the scientists were able to demonstrate the black holes exhibited a property known as “spin”.

“This is the first time that we have evidence that the black holes may not be aligned, giving us just a tiny hint that pairs of black holes may form in dense stellar clusters,” Professor Blair said.

Postdoctoral Fellow Qi Chu, from UWA’s School of Physics, is part of a team led by OzGrav Chief Investigator Professor Linqing Wen that is racing to create faster ways to crunch the LIGO data to minimise the time between the gravitational waves hitting earth and an alert being sent out for follow-up observations.

“The LIGO detector lets us feel the gravitational wave, and we are on a mission to see the source of the event by looking through powerful telescopes,” Ms Chu said.

An international group of researchers, including the Australian International Gravitational Research Centre, is also investigating how to fine-tune the sensitivity of the gravitational waves detector, leading to improved detection of future gravitational waves and electromagnetic observational, and potentially more exotic sources.